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      <title>Netty 是如何处理高并发的 - 交互式测验</title>
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          <div class="quiz-container">
            <div class="quiz-header">
              <h1>Netty 是如何处理高并发的 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
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  {
    "question": "Netty 能够高效处理大量并发连接的核心机制之一是非阻塞 I/O (NIO)。根据文档描述，NIO 主要是通过什么方式来提升性能的？",
    "options": [
      "为每一个客户端连接都创建一个独立的线程，实现真正的并行处理。",
      "允许单线程通过事件驱动机制处理多个连接，从而减少线程和上下文切换的开销。",
      "依赖操作系统内核进行数据零拷贝，完全避免数据在用户态的传输。",
      "通过增加TCP协议栈的缓冲区大小来强制提高网络吞吐量。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "NIO 的核心优势在于其非阻塞和事件驱动的特性。它允许一个线程（或少量线程）管理多个网络连接。当没有数据可读/写时，线程不会被阻塞，而是可以去处理其他就绪的连接，这极大地减少了因线程创建、休眠和切换带来的系统开销。",
    "source": "文档中「1. 非阻塞 I/O（NIO）」部分",
    "hint": "文档中提到NIO允许“单线程处理多个连接”，并能“减少了线程切换和上下文切换的开销”。"
  },
  {
    "question": "在 Netty 的经典线程模型中，`EventLoopGroup` 通常分为 Boss 线程组和 Worker 线程组。它们各自的主要职责是什么？",
    "options": [
      "Boss 线程组负责接受客户端连接请求，Worker 线程组负责处理已连接通道的 I/O 操作。",
      "Boss 线程组负责处理所有的数据读写，Worker 线程组负责执行耗时的业务逻辑。",
      "Boss 线程组和 Worker 线程组共同负责接受连接和处理 I/O，以实现负载均衡。",
      "Worker 线程组负责接受连接，Boss 线程组负责关闭连接和回收资源。"
    ],
    "correctAnswerIndex": 0,
    "explanation": "这是一种职责分离的设计模式。Boss 线程组的角色类似“接待员”，专门负责处理客户端的连接请求，一旦连接建立成功，就将后续的 I/O 处理任务（如数据读写）转交给 Worker 线程组。Worker 线程组则像“工人”，专注于处理具体的业务数据。",
    "source": "文档中「3. 线程池优化」部分",
    "hint": "可以把这个模型想象成一个餐厅：一个“接待员”（Boss）负责迎接客人并引导入座，而多个“服务员”（Worker）则负责为已入座的客人点餐和上菜。"
  },
  {
    "question": "为了提升性能并降低GC（垃圾回收）压力，Netty 采用了独特的内存管理机制。这个机制的核心是什么？",
    "options": [
      "将所有网络数据都缓存在操作系统的内核空间，避免用户态和内核态的切换。",
      "完全依赖 Java 虚拟机的自动垃圾回收（GC）来高效管理所有内存对象。",
      "使用自定义的内存池（通过 `ByteBuf`）来管理缓冲区，通过重用缓冲区减少内存的频繁分配和回收。",
      "强制使用 Java 的堆外内存（Direct Memory），以完全避免GC的介入。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "Netty 的 `ByteBuf` 和其背后的内存池技术是性能优化的关键。相比于每次需要时都创建新的字节数组，内存池会预先分配一块大的内存，并将其划分为多个小块。当需要缓冲区时，从池中获取；使用完毕后，归还到池中。这种重用机制显著减少了 JVM 的GC负担，从而提升了应用的稳定性和性能。",
    "source": "文档中「4. 高效的内存管理」部分",
    "hint": "文档中提到了一个关键词：“内存池”，并指出它能够“重用缓冲区，降低了 GC 压力”。"
  },
  {
    "question": "在进行性能优化时，合理配置 Worker 线程组的大小至关重要。根据文档中的代码示例和说明，当使用 `new NioEventLoopGroup()` 无参构造函数时，默认创建的 Worker 线程数通常是多少？",
    "options": [
      "等于 CPU 的核心数。",
      "CPU 核心数的 2 倍。",
      "固定为 16 个线程。",
      "与 Boss 线程组的数量保持一致（通常为1）。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档中的代码注释明确指出 `new NioEventLoopGroup()` 默认创建的线程数是 CPU 核心数的 2 倍。这是一个经验性的默认值，旨在充分利用多核 CPU 的处理能力，同时为可能存在的 I/O 等待留出处理其他任务的线程。",
    "source": "文档中「1. 合理配置线程池」部分",
    "hint": "请仔细阅读文档中关于 `workerGroup` 初始化的那行代码后面的注释。"
  },
  {
    "question": "Netty 的 `ChannelPipeline` 是一个重要的组件。根据文档中“合理使用 Pipeline”的性能优化策略，以下哪种做法是推荐的？",
    "options": [
      "将所有业务逻辑都集中在唯一一个庞大的 Handler 中，以减少对象创建和方法调用的开销。",
      "将复杂的业务逻辑分解为多个功能单一、职责清晰的 Handler，并按顺序添加到 Pipeline 中。",
      "只在 Pipeline 中添加编解码器，所有业务逻辑应在 Pipeline 外部通过异步回调来处理。",
      "为了极致性能，应避免使用 Pipeline，直接在 `Channel` 上进行读写操作。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档建议将处理逻辑合理地分布在 `ChannelPipeline` 中，将复杂的业务逻辑分解为多个简单的处理器。这种“责任链”模式使得代码结构更清晰、更易于维护和复用，同时也有利于 Netty 的事件分发和处理效率。",
    "source": "文档中「5. 合理使用 Pipeline」部分",
    "hint": "文档建议“避免在单个处理器中执行过多操作”，并提倡“将复杂的业务逻辑分解”。"
  },
  {
    "question": "为了避免 I/O 线程阻塞并提升应用的并发处理能力，Netty 推荐使用其异步操作模型。以下哪个代码片段最能体现这一特性？",
    "options": [
      "`channel.writeAndFlush(message).sync();`",
      "`boolean result = channel.isActive();`",
      "`new Thread(() -> channel.writeAndFlush(message)).start();`",
      "`channel.writeAndFlush(message).addListener(future -> { ... });`"
    ],
    "correctAnswerIndex": 3,
    "explanation": "使用 `.addListener(...)` 模式是 Netty 异步编程的核心。`writeAndFlush` 方法会立即返回一个 `ChannelFuture` 对象，而不会等待操作完成。通过给这个 `Future` 添加监听器，我们可以在操作完成（无论成功或失败）时执行相应的回调逻辑，从而避免了当前线程的阻塞。",
    "source": "文档中「6. 使用异步操作」部分",
    "hint": "异步操作的关键在于“不阻塞当前线程，而是在操作完成后得到通知”。哪个选项展示了这种“注册回调”的模式？"
  }
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            const wrongCount = answeredCount - correctCount;
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            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

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                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
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                '<div class="score-card">' +
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                '<div class="score-card">' +
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                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
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                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  